1. Field of the Invention
The present invention relates to a magnetic recording medium and, more particularly, to a magnetic recording medium excellent in durability and reliability.
2. Description of the Related Art
In recent years, magnetic recording media, i.e., magnetic tapes such as an audio tape and a video tape or magnetic disks such as a floppy disk must satisfy requirements for a high-speed data access and a high recording density in addition to excellent electromagnetic conversion characteristics.
As a method of increasing a recording density of a magnetic recording medium, a packing density of a magnetic powder in a magnetic layer is attempted to be increased, and a recording density in the widthwise or longitudinal direction of tracks is attempted to be increased utilizing servo techniques. As a method of increasing a data access speed of a magnetic recording medium, an increase in relative speed between a magnetic head and the magnetic recording medium is attempted. In order to satisfy the requirements for a high-speed data access and a high recording density, therefore, the packing density of the magnetic powder in the magnetic layer must be increased, and the relative speed between the magnetic head and the magnetic recording medium must be increased.
When a packing density of a magnetic powder in a magnetic layer is increased, however, a ratio of a binder resin to the magnetic powder in the magnetic layer is relatively decreased. For this reason, adhesion strength between a support and the magnetic layer is degraded. When a relative speed between a magnetic head and a magnetic recording medium having the above magnetic layer is increased, the magnetic layer peels from the support within a short period of time due to contact between the magnetic head and the magnetic layer. Foreign substances such as dust produced upon peeling of the magnetic layer from the support are attached to the surface of the magnetic layer. These foreign substances cause an error in the operation of the magnetic recording medium. As a result, reliability of the magnetic recording medium is greatly impaired.
In order to solve the above problems, for example, Published Japanese Unexamined Patent Application No. 60-163234 discloses a method of manufacturing a magnetic recording medium, wherein an intermediate layer is formed on a nonmagnetic support having an average value of surface roughness values (Ra) of 0.01 .mu.m or more, and then a magnetic layer is formed on this intermediate layer, thereby improving adhesion strength between the magnetic layer and the nonmagnetic support. That is, according to this method, surface roughness of the nonmagnetic support is increased to increase a contact area between the intermediate layer and the nonmagnetic support, thereby improving the adhesion strength.
It is thus possible to improve the adhesion strength between the support and the magnetic layer by increasing surface roughness of the support. When the surface roughness of the support is increased, however, the surface of the magnetic layer conforms to the roughness of the support and is reduced in smoothness. For this reason, a good head touch between the magnetic layer and the magnetic head cannot be obtained. Since the surface roughness of the support is closely associated with the smoothness of the magnetic layer, it is very difficult to improve the smoothness of the surface of the magnetic layer while the surface roughness of the support is increased to improve the adhesion strength between the support and the magnetic layer.